1. Field of the Invention
The present invention relates to liquid containers and image forming apparatuses, and more particularly to an image forming apparatus having recording heads for jetting liquid droplets and a liquid container for containing liquid to be supplied to the recording heads.
2. Description of the Related Art
There are image forming apparatuses such as printers, fax machines, copiers, plotters, and multifunction peripherals including functions of these devices. An inkjet recording apparatus is known as an example of an image forming apparatus of a liquid jet recording method using recording heads for jetting ink droplets. Such an image forming apparatus of a liquid jet recording method forms images (record and print may be used synonymously as form) by jetting ink droplets from recording heads onto a conveyed sheet (the sheet is not limited to a paper sheet; the sheet may be any sheet onto which ink droplets or other types of liquid can adhere such as an OHP transparency film; the sheet may also be referred to as a recording medium, a recording sheet, etc.). There are several types of image forming apparatuses of a liquid jet recording method. One example is a serial type image forming apparatus that forms images by jetting liquid droplets while moving the recording heads in a main scanning direction. Another example is a line type image forming apparatus that uses line type heads to form images by jetting liquid droplets while the recording heads do not move.
In the present application, an image forming apparatus of a liquid jet recording method means an apparatus that forms images by jetting liquid onto a medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc. Forming images on a medium means forming images having meaning (such as characters and figures) and forming images without any meaning (such as patterns, e.g., merely jetting liquid droplets onto a medium). Ink is not limited to what is generally referred to as ink; ink refers to any kind of liquid that can be used for forming images, such as recording liquid and fixing process liquid; examples of ink are DNA samples, resist, and pattern material.
There is demand for an image forming apparatus of a liquid jet recording method with high image forming throughput, i.e., high image forming speed. Accordingly, there is known a method of supplying ink from a large capacity ink cartridge in the apparatus main unit (main tank), to a sub tank (also referred to as a head tank or a buffer tank) via a tube.
A liquid container used as the main tank or the ink cartridge is, for example, an ink cartridge including an ink pack and a hard case for accommodating the ink pack. Plural ribs are provided inside the hard case for holding the periphery of the ink pack. The ink pack is held to substantially maintain a certain shape, so that it does not deform by a large amount even when shaken or dropped. Accordingly, the ink pack is prevented from being damaged (see patent document 1).
Patent Document 1: Japanese Laid-Open Patent Application No. 2001-105619
For example, an ink cartridge includes a flexible ink pack containing ink and an outer container such as a hard case accommodating the ink pack. The ink is supplied from the ink cartridge to the main unit of an image forming apparatus. The ink pack gradually deflates as the ink is consumed. When the ink pack finally becomes flat, if the ink pack is not neatly deflated, a large amount of ink may remain in the ink pack without being used. Accordingly, a large amount of ink may be left over.